The transcript from the video "1.2. [Lecture] Pharo: An Immersive Object-Oriented System" of the Pharo MOOC says:
Every graphic element of Pharo that you click on... - With Cmd+Shift+Option, - you'll get a little menu around the graphic element.
I don't get this halo directly, by presing
Shift, which can be a little confusing. What I get is a contextual menu that let's me to select the halo after that. (image above).
After that I need to go to the
add halo menu. It's kind of indirect, compared with the previous behavior.
The combination that works is `Shift`+`Alt`+`MiddleClick`. (Thanks to Ben Coman, for the answer).